The invention relates to a radar method used in a motor vehicle for an automatic, intelligent traffic flow control (AICC).
The characteristics and design of known radar devices in motor vehicles are essentially defined by the use of pulse radar. The known systems make use of involved and cost-intensive multipath systems to detect several measuring variables,.
A high-resolution radar method is described in the previously filed German patent application 197 32 509.2, which is based on a frequency-modulated, continuous-wave (FM-CW) method with saw-tooth modulation to achieve a simultaneous resolution of the radar scene with respect to distance and relative speed. With this method, the radar echo is mixed at the transmitting reference to form the baseband signal. The method is distinguished in that:
The baseband signal of each modulation period is digitized in an analog/digital converter and is converted to distance/time values by means of a N-point Fourier Transformation; PA1 this conversion is repeated for M modulation periods that follow successively in time; PA1 the determined distance values for each modulation period are stored in a line, assigned to the respective modulation period, of a two-dimensional data memory; PA1 the stored distance/time values are subjected in columns to an M-point Fourier Transformation to form relative speed values and that a distance/speed matrix of the observed radar scene is generated in this way. PA1 This method provides for a frequency-dependent and thus also distance-dependent level compensation in the analog portion of the radar sensor, or a frequency limitation of the baseband signals to higher frequencies by utilizing an anti-aliasing filter that is connected in series before the A/D converter. One embodiment of the method provides that of the N distance/time values, determined with the N-pointed Fourier Transformation, only N.sub.R &lt;N/2 values are stored and processed for the subsequent signal processing. The Fourier Transformations used (e.g. the Fast Fourier Transformation (FFT)) operate with suitable data windows to reduce minor lobes to a preset value for the resolution cells of the distance/speed matrix.